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Gut microbes may put barrier between species

Removing bacteria in wasps saves crossbred offspring from death

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12:47pm, July 2, 2013

Nasonia  vitripennis (shown) and N. giraulti wasps may remain distinct  species because of their gut microbes, not just genetics, a new study suggests. 

SNOWBIRD, Utah — The bazillion microbes teeming inside bigger creatures may be an overlooked but vital part of what divides the big organisms into species.

Two species of jewel wasp (Nasonia giraulti and N. vitripennis) stay separate in large part because most male larvae die when the species crossbreed, says Seth Bordenstein of Vanderbilt University in Nashville. Biologists have long blamed the demise on lethal incompatibilities in DNA. Yet using antibiotics to kill off the gut bacteria in the supposedly doomed hybrids rescued many of them, he reported June 23 at the Evolution 2013 conference. In this lab test, the germ-free hybrid larvae survived about as well as purebred germ-free larvae.

In a further test, colleague Robert Brucker gave microbe-free hybrid larvae two kinds of gut bacteria from regular hybrids. Survival rates plummeted.

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